RF treatment apparatus

ABSTRACT

An RF treatment apparatus includes a catheter with a catheter lumen. A removable needle electrode is positioned in the catheter lumen in a fixed relationship to the catheter. The needle electrode includes a needle lumen and a needle electrode distal end. A removable introducer is slidably positioned in the needle lumen. The introducer includes an introducer distal end. A first sensor is positioned on a surface of the needle electrode or the insulator. An RF power source is coupled to the needle electrode and a return electrode. An insulator sleeve is slidably positioned around the electrode and includes a second sensor. Resources are associated with the electrodes, sensors as well as the RF power source for maintaining a selected power at the electrode independent of changes in current or voltage.

This application is a divisional of application Ser. No. 08/295,166,filed Aug. 24, 1994, now U.S. Pat. No. 5,599,345, which is is acontinuation-in-part of U.S. Pat. application Ser. No. 08/148,439 filedNov. 8, 1993, now U.S. Pat. No. 5,548,597, entitled "DEVICE FOR TREATINGCANCER AND NON-MALIGNANT TUMORS AND METHODS", by Edwards et al. which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to an apparatus for the treatment andablation of body masses, such as tumors, and more particularly, to an RFtreatment system suitable for multi-modality treatment with an infusiondelivery device, catheter, removable electrode, insulator sleeve andintroducer, all housed in the catheter. The system maintains a selectedpower at an electrode what is independent of changes in current orvoltage.

2. Description of the Related Art

Current open procedures for treatment of tumors are extremely disruptiveand cause a great deal of damage to healthy tissue. During the surgicalprocedure, the physician must exercise care in not cutting the tumor ina manor that creates seeding of the tumor, resulting in metastasis. Inrecent years, development of products has been directed with an emphasison minimizing the traumatic nature of traditional surgical procedures.

There has been a relatively significant amount of activity in the areaof hyperthermia as a tool for treatment of tumors. It is known thatelevating the temperature of tumors is helpful in the treatment andmanagement of cancerous tissues. The mechanisms of selective cancer celleradication by hyperthermia are not completely understood. However, fourcellular effects of hyperthermia on cancerous tissue have been proposed,(i) changes in cell or nuclear membrane permeability or fluidity, (ii)cytoplasmic lysomal disintegration, causing release of digestiveenzymes, (iii) protein thermal damage affecting cell respiration and thesynthesis of DNA or RNA and (iv) potential excitation of immunologicsystems. Treatment methods for applying heat to tumors include the useof direct contact radio-frequency (RF) applicators, microwave radiation,inductively coupled RF fields, ultrasound, and a variety of simplethermal conduction techniques.

Among the problems associated with all of these procedures is therequirement that highly localized heat be produced at depths of severalcentimeters beneath the surface of the body. Certain techniques havebeen developed with microwave radiation and ultrasound to focus energyat various desired depths. RF applications may be used at depth duringsurgery. However, the extent of localization is generally poor, with theresult that healthy tissue may be harmed. Induction heating gives riseto poor localization of the incident energy as well. Although inductionheating may be achieved by placing an antenna on the surface of thebody, superficial eddy currents are generated in the immediate vicinityof the antenna, when it is driven using RF current, and unwanted surfaceheating occurs with little heating delivered to the underlying tissue.

Thus, non-invasive procedures for providing heat to internal tumors havehad difficulties in achieving substantial specific and selectivetreatment.

Hyperthermia, which can be produced from an RF or microwave source,applies heat to tissue but does not exceed 45 degrees C so that normalcells survive. In thermotherapy, heat energy of greater than 45 degreesC is applied, resulting in histological damage, desiccation and thedenaturization of proteins. Hyperthermia has been applied more recentlyfor therapy of malignant tumors. In hyperthermia, it is desirable toinduce a state of hyperthermia that is localized by interstitial currentheating to a specific area while concurrently insuring minimum thermaldamage to healthy surrounding tissue. Often, the tumor is locatedsubcutaneously and addressing the tumor requires either surgery,endoscopic procedures or external radiation. It is difficult toexternally induce hyperthermia in deep body tissue because currentdensity is diluted due to its absorption by healthy tissue.Additionally, a portion of the RF energy is reflected at the muscle/fatand bone interfaces which adds to the problem of depositing a knownquantity of energy directly on a small tumor.

Attempts to use interstitial local hyperthermia have not proven to bevery successful. Results have often produced nonuniform temperaturesthroughout the tumor. It is believed that tumor mass reduction byhyperthermia is related to thermal dose. Thermal dose is the minimumeffective temperature applied throughout the tumor mass for a definedperiod of time. Because blood flow is the major mechanism of heat lossfor tumors being heated, and blood flow varies throughout the tumor,more even heating of tumor tissue is needed to ensure effectivetreatment.

The same is true for ablation of the tumor itself through the use of RFenergy. Different methods have been utilized for the RF ablation ofmasses such as tumors. Instead of heating the tumor it is ablatedthrough the application of energy. This process has been difficult toachieve due to a variety of factors including, (i) positioning of the RFablation electrodes to effectively ablate all of the mass, (ii)introduction of the RF ablation electrodes to the tumor site and (iii)controlled delivery and monitoring of RF energy to achieve successfulablation without damage to non-tumor tissue.

There have been a number of different treatment methods and devices forminimally invasively treating tumors. One such example is an endoscopethat produces RF hyperthermia in tumors, as disclosed in U.S. Pat. No.4,920,978. A microwave endoscope device is described in U.S. Pat. No.4,409,993. In U.S. Pat. No. 4,920,978, an endoscope for RF hyperthermiais disclosed.

In U.S. Pat. No. 4,763,671 (the "'671 patent"), a minimally invasiveprocedure utilizes two catheters that are inserted interstitially intothe tumor. The catheter includes a hard plastic support member. Aroundthe support member is a conductor in the form of an open mesh. A layerof insulation is secured to the conductor with adhesive beads. It coversall of the conductor except a preselected length which is notadjustable. Different size tumors can not be treated with the sameelectrode. A tubular sleeve is introduced into the support member andhouses radioactive seeds. The device of the '671 patent fails to providefor the introduction of a fluidic medium, such as a chemotherapeuticagent, to the tumor for improved treatment. The size of the electrodeconductive surface is not variable. Additionally, the device of the '671patent is not capable of maintaining a preselected level of power thatis independent of changes in voltage or current.

In U.S. Pat. No. 4,565,200 (the "'200 patent"), an electrode system isdescribed in which a single entrance tract cannula is used to introducean electrode into a selected body site. The device of the '200 patent islimited in that the single entrance tract fails to provide for theintroduction, and removal of a variety of inserts, including but notlimited to an introducer, fluid infusion device and insulation sleeve.Additionally, the device of the '200 patent fails to provide for themaintenance of a selected power independent of changes in current orvoltage.

There is a need for an RF treatment device which provides formulti-modality treatment of selected tissue sites which includes acatheter with a single entrance tract for an RF treatment electrode, anintroducer, an insulator sleeve and a fluid infusion device. It woulddesirable to provide an RF treatment apparatus which maintains aselected power at the electrode independent of changes in voltage orcurrent.

SUMMARY

Accordingly, an object of the invention is to provide an RF treatmentapparatus which has a catheter insert adapted to receive interchangeableintroducers and electrodes positioned in the insert.

Another object of the invention is to provide an RF treatment apparatuswhich has a catheter insert with interchangeable introducers andelectrodes, and resources to maintain the electrode at a selected powerirrespective of changes in current or voltage.

Still a further object of the invention is to provide an RF treatmentapparatus, which maintains an electrode at a selected power independentof changes in current and voltage, and operates in the bipolar mode.

Yet another object of the invention is to provide an RF treatmentapparatus with a needle electrode removably positioned in a catheterlumen, with resources to maintain the electrode at a selected powerirrespective of changes in current or voltage.

Another object of the invention is to provide an RF treatment apparatuswhich includes a removable introducer that is slidably positioned in aneedle lumen, and resources are incorporated which maintain a selectedpower of the electrode independent of changes in current or voltage.

A further object of the invention is to provide an RF treatmentapparatus which includes an infusion device, catheter and a needleelectrode, both removable from the infusion device which can remainpositioned in a body structure to permit the introduction of achemotherapeutic agent directly through the infusion device, or througha separate delivery device positioned in the lumen of the infusiondevice.

These and other objects of the invention are achieved with an RFtreatment apparatus that includes a catheter with a catheter lumen. Aremovable needle is positioned in the catheter lumen in a fixedrelationship to the catheter. The needle electrode includes a needlelumen and a needle electrode distal end. A removable introducer isslidably positioned in the needle lumen. The introducer includes anintroducer distal end. A return electrode can be included that attachesto the patient's skin. A first sensor, which can be a thermal sensor, ispositioned on a surface of the electrode or the introducer. An RF powersource is coupled to the needle electrode. Associated with the RF powersource, return electrode and first sensor are resources for maintaininga selected power at the electrode that is independent of changes incurrent or voltage.

In another embodiment of the invention, the RF treatment apparatusincludes a catheter with a catheter lumen. An insert is removablypositioned in the catheter lumen, in a fixed relationship to thecatheter. The insert includes an insert lumen and an insert distal end.A removable electrode is positioned in the insert. It has an electrodedistal end that advances out of the insert distal end and introduces RFtreatment energy along a conductive surface of the electrode. A firstsensor is positioned on a surface of the electrode or insert. An RFpower source is coupled to the electrode. Associated with the RF powersource, a return electrode and first sensor are resources that maintaina selected power at the electrode which is independent of a change involtage or current.

In a further embodiment of the invention, the RF treatment apparatusincludes an infusion device with an infusion device lumen. A catheter,including a catheter lumen, is at least partially positioned in theinfusion device lumen and is removable therefrom. A removable needleelectrode is positioned in the catheter lumen in a fixed relationship tothe catheter. The needle electrode includes a needle lumen. Aninsulator, with an insulator distal end, is in a surroundingrelationship to the treatment needle electrode. The insulator isslidably positioned along a longitudinal axis of the treatment needleelectrode and defines a needle electrode conductive surface that beginsat the insulator distal end. A first sensor is positioned on a surfaceof the insulator or electrode. An RF power source is coupled to theneedle electrode. Resources are associated with the RF power source, areturn electrode and the first sensor for maintaining a selected powerat the electrode that is independent of changes in voltage or current.

With the RF treatment apparatus of the invention, an insert or treatmentneedle is removably attached to a catheter and positioned in thecatheter lumen, or the catheter is removably attached to the infusiondevice and positioned in the infusion device lumen. An introducer can beslidably positioned in the insert lumen initially, to assist in theintroduction of the catheter and insert into a body structure. Theintroducer is then removed and the treatment needle substituted in itsplace. Temperature readings are taken adjacent to the tissue site in thevicinity of the electrode. Resources control the amount of energysupplied to the treatment site so that RF energy is delivered at lowenough power so that the tissue at the electrode is not desiccated, butsufficient enough to kill the cells of the tumor.

An electrode treatment device, consisting of catheter, insulator, andeither an electrode or an introducer, is removed from an infusion devicefollowing the delivery of RF energy to the tissue site. The infusiondevice remains positioned adjacent to or in the tumor. This permits thecontinued introduction of a chemotherapeutic agent to the tumor site, orsubsequently, the catheter with electrode can be reintroduced andfurther RF energy delivered to the tumor site.

Hardware and software, collectively "resources" maintain a selectedpower at the electrode include a power supply, power circuits,controller, user interface and display, a device to calculate power andimpedance, current and voltage sensors and a temperature measurementdevice. The controller can be under microprocessor control. Imaging ofthe tumor, through ultrasound, CT scanning, and the like, can beutilized to first define the boundaries of the tumor mass. Images of thetumor are then imported to a display. Individual electrode needles arethereafter positioned in or surround the tumor, and RF energy is thenslowly delivered to the tumor. Prior treatment planning of the tumorassists in the effective delivery of RF treatment energy. Throughimaging, tissue characterization by monitoring the process, is achieved.The electrodes are used in the bipolar mode.

An electrode can be removed from the catheter and placed at a differentlocation than the catheter to measure temperature, and deliver RFenergy. Multiple electrodes are introduced through their respectivecatheters to tumor sites. Tumor sites are treated, through hyperthermiaor ablation, selectively through the controlled delivery of RF energy.Temperature is monitored, and through the resources, a selected level ofpower is maintained independent of changes in voltage or current. Avariety of different devices can be positioned and removed in thecatheter. These include, introducers and electrodes. The treatmentdevice of the invention permits a wide range of tumor treatment devicesto be introduced to the tumor site for multi-modality evaluation andtreatment purposes. The catheter or infusion device can remainpositioned at the tumor site for an extended period for later treatmentof RF energy or introduction of a chemotherapeutic agent.

DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is a cross-sectional view of an RF treatment apparatus of theinvention.

FIG. 1(b) is a close up cross-sectional view of the distal end of the RFtreatment apparatus of FIG. 1(a).

FIG. 1(c) is a close up cross-sectional view of the RF treatmentapparatus of FIG. 1(a), illustrating the proximal end of the insulationsleeve and a thermocouple associated with the insulation sleeve.

FIG. 1(d) is a close up cross-sectional view of the RF treatmentapparatus of FIG. 1(a), illustrating the proximal end of the RFtreatment apparatus of FIG. 1(a).

FIG. 2 is an exploded view of an RF treatment apparatus of theinvention.

FIG. 3 is a cross-sectional view of the RF treatment apparatus of theinvention illustrating the electrode, insulation sleeve and theassociated thermal sensors.

FIG. 4(a) is a perspective view of the RF treatment apparatus of theinvention with the infusion device mounted at the distal end of thecatheter.

FIG. 4(b) is a perspective view of the RF treatment apparatus of FIG.4(a) illustrating the removal of the catheter, and electrode attached tothe distal end of the electrode, from the infusion device which is leftremaining in the body.

FIG. 5(a) is a perspective view of the RF treatment apparatus of theinvention with the electrode mounted at the distal end of the catheter.

FIG. 5(b) is a perspective view of the RF treatment apparatus of FIG.5(a) illustrating the removal of the introducer from the lumen of theelectrode.

FIG. 6(a) is a perspective view of the RF treatment apparatus of theinvention with the introducer removed from the lumen of the electrode.

FIG. 6(b) is a perspective view of the apparatus of FIG. 6(a)illustrating the removal of the electrode from the catheter, leavingbehind the insulation sleeve.

FIG. 7(a) is a perspective view of the RF ablation apparatus of theinvention with the insulation sleeve positioned in a surroundingrelationship to the electrode which is mounted to the distal end of thecatheter.

FIG. 7(b) is a perspective view of the RF ablation apparatus of FIG.7(a) illustrating the removal of the insulation sleeve from theelectrode.

FIG. 7(c) is a perspective view of the insulation sleeve after it isremoved from the electrode.

FIG. 8(a) is a perspective view illustrating the attachment of a syringeto the device of FIG. 6(a).

FIG. 8(b) is a perspective view of a syringe, containing a fluid mediumsuch as a chemotherapeutic agent, attached to the RF ablation apparatusof FIG. 6(a).

FIG. 9 is a block diagram of an RF treatment system of the invention.

FIGS. 10(a-1)-10(a-2) are a schematic diagram of a power supply suitableuseful with the invention.

FIG. 10(b) is a schematic diagram of a voltage sensor suitable usefulwith the invention.

FIG. 10(c) is a schematic diagram of a current sensor suitable usefulwith the invention.

FIG. 10(d) is a schematic diagram of power computing circuits suitableuseful with the invention.

FIG. 10(e) is a schematic diagram of an impedance computing circuitsuitable useful with the invention.

FIG. 10(f) is a schematic diagram of a power control device suitableuseful with the invention.

FIGS. 10(g-1) to 10(g-4) are a schematic diagram of an eight channeltemperature measurement suitable useful with the invention.

FIGS. 10(h-1) to 10(h-2) are a schematic diagram of a power andtemperature control circuit useful with the invention.

FIG. 11 is a block diagram of an embodiment of the invention whichincludes a microprocessor.

FIG. 12 illustrates the use of two RF treatment apparatus, such as theone illustrated in FIG. 1(a), that are used in a bipolar mode.

FIG. 13 is a planar view of a stylet ablation device of this invention.

FIG. 14 is fragmentary cross-sectional view of the tip of the stylet ofFIG. 1 with the electrode extended from the tip.

FIG. 15 is a schematic view showing use of an embodiment with a shapememory electrode preformed into a curved shape to ablate a tissue mass.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1(a), 1(b), 1(c), 2 and 3 an RF treatmentapparatus 10 is illustrated which can be used to ablate a selectedtissue mass, including but not limited to a tumor, or treat the mass byhyperthermia. Treatment apparatus 10 includes a catheter 12 with acatheter lumen in which different devices are introduced and removed. Aninsert 14 is removably positioned in the catheter lumen. Insert 14 canbe an introducer, a needle electrode, and the like.

When insert 14 is an introducer, including but not limited to a guidingor delivery catheter, it is used as a means for puncturing the skin ofthe body, and advancing catheter 12 to a desired site. Alternatively,insert 14 can be both an introducer and an electrode adapted to receiveRF current for tissue ablation and hyperthermia.

If insert 14 is not an electrode, then a removable electrode 16 ispositioned in insert 14 either during or after treatment apparatus 10has been introduced percutaneously to the desired tissue site. Electrode16 has an electrode distal end that advances out of an insert distalend. In this deployed position, RF energy is introduced to the tissuesite along a conductive surface of electrode 16.

Electrode 16 can be included in treatment apparatus 10, and positionedwithin insert 14, while treatment apparatus 10 is being introduced tothe desired tissue site. The distal end of electrode 16 can havesubstantially the same geometry as the distal end of insert 14 so thatthe two ends are essentially flush. Distal end of electrode 16, whenpositioned in insert 14 as it is introduced through the body, serves toblock material from entering the lumen of insert 14. The distal end ofelectrode 16 essentially can provide a plug type of function.

Electrode 16 is then advanced out of a distal end of insert 14, and thelength of an electrode conductive surface is defined, as explainedfurther in this specification. Electrode 16 can advance out straight,laterally or in a curved manner out of distal end of insert 14. Ablativeor hyperthermia treatment begins when two electrodes 16 are positionedclosely enough to effect bipolar treatment of the desired tissue site ortumor. A return electrode attaches to the patients skin. Operating in abipolar mode, selective ablation of the tumor is achieved. However, itwill be appreciated that the present invention is suitable for treating,through hyperthermia or ablation, different sizes of tumors or masses.The delivery of RF energy is controlled and the power at each electrodeis maintained, independent of changes in voltage or current. Energy isdelivered slowly at low power. This minimizes desiccation of the tissueadjacent to the electrodes 16, permitting a wider area of even ablation.In one embodiment, 8 to 14 W of RF energy is applied in a bipolar modefor 10 to 25 minutes. An ablation area between electrodes 16 of about 2to 6 cm is achieved.

Treatment apparatus 10 can also include a removable introducer 18 whichis positioned in the insert lumen instead of electrode 16. Introducer 18has an introducer distal end that also serves as a plug, to minimize theentrance of material into the insert distal end as it advances through abody structure. Introducer 18 is initially included in treatmentapparatus, and is housed in the lumen of insert 14, to assist theintroduction of treatment apparatus 10 to the desired tissue site. Oncetreatment apparatus 10 is at the desired tissue site, then introducer 18is removed from the insert lumen, and electrode 16 is substituted in itsplace. In this regard, introducer 18 and electrode 16 are removable toand from insert 14.

Also included is an insulator sleeve 20 coupled to an insulator slide22. Insulator sleeve 20 is positioned in a surrounding relationship toelectrode 16. Insulator slide 22 imparts a slidable movement of theinsulator sleeve along a longitudinal axis of electrode 16 in order todefine an electrode conductive surface what begins at an insulatorsleeve distal end.

A thermal sensor 24 can be positioned in or on electrode 16 orintroducer 18. A thermal sensor 26 is positioned on insulator sleeve 20.In one embodiment, thermal sensor 24 is located at the distal end ofintroducer 18, and thermal sensor 26 is located at the distal end ofinsulator sleeve 20, at an interior wall which defines a lumen ofinsulator sleeve 20. Suitable thermal sensors include a T typethermocouple with copper constantene, J type, E type, K type,thermistors, fiber optics, resistive wires, thermocouples IR detectors,and the like. It will be appreciated that sensors 24 and 26 need not bethermal sensors.

Catheter 12, insert 14, electrode 16 and introducer 18 can be made of avariety of materials. In one embodiment, catheter 12 is black anodizidaluminum, 0.5 inch, electrode 16 is made of stainless steel, 18 gauge,introducer 18 is made of stainless steel, 21 gauge, and insulator sleeve20 is made of polyimide.

By monitoring temperature, RF power delivery can be accelerated to apredetermined or desired level. Impedance is used to monitor voltage andcurrent. The readings of thermal sensors 24 and 26 are used to regulatevoltage and current that is delivered to the tissue site. The output forthese sensors is used by a controller, described further in thisspecification, to control the delivery of RF energy to the tissue site.Resources, which can be hardware and/or software, are associated with anRF power source, coupled to electrode 16 and the return electrode. Theresources are associated with thermal sensors 24 and 25, the returnelectrode as well as the RF power source for maintaining a selectedpower at electrode 16 independent of changes in voltage or current.Thermal sensors 24 and 26 are of conventional design, including but notlimited to thermistors, thermocouples, resistive wires, and the like.

Electrode 16 is preferably hollow and includes a plurality of fluiddistribution ports 28 from which a variety of fluids can be introduced,including electrolytic solutions, chemotherapeutic agents, and infusionmedia.

A specific embodiment of the RF treatment device 10 is illustrated inFIG. 2. Included is an electrode locking cap 28, an RF coupler 30, anintroducer locking cap 32, insulator slide 22, catheter body 12,insulator retainer cap 34, insulator locking sleeve 36, a luer connector38, an insulator elbow connector 40, an insulator adjustment screw 42, athermocouple cable 44 for thermal sensor 26, a thermocouple cable 46 forthermal sensor 24 and a luer retainer 48 for an infusion device 50.

In another embodiment of RF treatment apparatus 10, electrode 16 isdirectly attached to catheter 12 without insert 14. Introducer 18 isslidably positioned in the lumen of electrode 16. Insulator sleeve 20 isagain positioned in a surrounding relationship to electrode 16 and isslidably moveable along its surface in order to define the conductivesurface. Thermal sensors 24 and 26 are positioned at the distal ends ofintroducer 18 and insulator sleeve 20. Alternatively, thermal sensor 24can be positioned on electrode 16, such as at its distal end. The distalends of electrode 16 and introducer 18 can be sharpened and tapered.This assists in the introduction of RF treatment apparatus to thedesired tissue site. Each of the two distal ends can have geometriesthat essentially match. Additionally, distal end of introducer 18 can anessentially solid end in order to prevent the introduction of materialinto the lumen of catheter 16.

In yet another embodiment of RF treatment apparatus 10, infusion device50 remains implanted in the body after catheter 12, electrode 16 andintroducer 18 are all removed. This permits a chemotherapeutic agent, orother infusion medium, to be easily introduced to the tissue site overan extended period of time without the other devices of RF treatmentapparatus 10 present. These other devices, such as electrode 16, can beinserted through infusion device 50 to the tissue site at a later timefor hyperthermia or ablation purposes. Infusion device 50 has aninfusion device lumen and catheter 12 is at least partially positionedin the infusion device lumen. Electrode 16 is positioned in the catheterlumen, in a fixed relationship to catheter 12, but is removable from thelumen. Insulator sleeve 20 is slidably positioned along a longitudinalaxis of electrode 16. Introducer 18 is positioned in a lumen ofelectrode 16 and is removable therefrom. A power source is coupled toelectrode 16. Resources are associated with thermal sensors 24 and 26,voltage and current sensors that are coupled to the RF power source formaintaining a selected power at electrode 16.

The distal end of RF treatment apparatus 10 is shown in FIG. 1(b).Introducer 18 is positioned in the lumen of electrode 16, which can besurrounded by insulator sleeve 20, all of which are essentially placedin the lumen of infusion device 50. It will be appreciated, however,that in FIG. 1(b) insert 14 can take the place of electrode 16, andelectrode 16 can be substituted for introducer 18.

The distal end of insulator sleeve 20 is illustrated in FIG. 1(c).Thermal sensor 26 is shown as being in the form of a thermocouple. InFIG. 1 (d), thermal sensor 24 is also illustrated as a thermocouple thatextends beyond a distal end of introducer 18, or alternative a distalend of electrode 16.

Referring now to FIGS. 4(a) and 4(b), infusion device 50 is attached tothe distal end of catheter 12 and retained by a collar. The collar isrotated, causing catheter 12 to become disengaged from infusion device50. Electrode 16 is attached to the distal end of catheter 12. Catheter12 is pulled away from infusion device 50, which also removes electrode16 from infusion device 50. Thereafter, only infusion device 50 isretained in the body. While it remains placed, chemotherapeutic agentscan be introduced through infusion device 50 to treat the tumor site.Additionally, by leaving infusion device 50 in place, catheter 12 withelectrode 16 can be reintroduced back into the lumen of infusion device50 at a later time for additional RF treatment in the form of ablationor hyperthermia.

In FIG. 5(a), electrode 16 is shown as attached to the distal end ofcatheter 12. Introducer 18 is attached to introducer locking cap 32which is rotated and pulled away from catheter 12. As shown in FIG. 5(b)this removes introducer 18 from the lumen of electrode 16.

Referring now to FIG. 6(a), electrode 16 is at least partiallypositioned in the lumen of catheter 12. Electrode locking cap 28 ismounted at the proximal end of catheter 12, with the proximal end ofelectrode 16 attaching to electrode locking cap 28. Electrode lockingcap 28 is rotated and unlocks from catheter 12. In FIG. 6(b), electrodelocking cap 28 is then pulled away from the proximal end of catheter 12,pulling with it electrode 16 which is then removed from the lumen ofcatheter 12. After electrode 16 is removed from catheter 12, insulatorsleeve 20 is locked on catheter 12 by insulator retainer cap 34.

In FIG. 7(a), insulator retainer cap 34 is unlocked and removed fromcatheter 12. As shown in FIG. 7(b), insulator sleeve 20 is then slid offof electrode 16. FIG. 7(c) illustrates insulator sleeve 20 completelyremoved from catheter 12 and electrode 16.

Referring now to FIGS. 8(a) and 8(b), after introducer 18 is removedfrom catheter 12, a fluid source, such as syringe 51, delivering asuitable fluid, including but not limited to a chemotherapeutic agent,attaches to luer connector 38 at the proximal end of catheter 12.Chemotherapeutic agents are then delivered from syringe 51 throughelectrode 16 to the tumor site. Syringe 51 is then removed from catheter12 by imparting a rotational movement of syringe 51 and pulling it awayfrom catheter 12. Thereafter, electrode 16 can deliver further RF powerto the tumor site. Additionally, electrode 16 and catheter 12 can beremoved, leaving only infusion device 50 in the body. Syringe 51 canthen be attached directly to infusion device 50 to introduce achemotherapeutic agent to the tumor site. Alternatively, other fluiddelivery devices can be coupled to infusion device 50 in order to have amore sustained supply of chemotherapeutic agents to the tumor site.

Once chemotherapy is completed, electrode 16 and catheter 12 can beintroduced through infusion device 50. RF power is then delivered to thetumor site. The process begins again with the subsequent removal ofcatheter 12 and electrode 16 from infusion device 50. Chemotherapy canthen begin. Once it is complete, further RF power can be delivered tothe tumor site. This process can be repeated any number of times for aneffective multi-modality treatment of the tumor site.

Referring now to FIG. 9, a block diagram of power source 52 isillustrated. Power source 52 includes a power supply 54, power circuits56, a controller 58, a power and impedance calculation device 60, acurrent sensor 62, a voltage sensor 64, a temperature measurement device66 and a user interface and display 68.

FIGS. 10(a) through 10(g) are schematic diagrams of power supply 54,voltage sensor 64, current sensor 62, power computing circuit associatedwith power and impedance calculation device 60, impedance computingcircuit associated with power and impedance calculation device 60, powercontrol circuit of controller 58 and an eight channel temperaturemeasurement circuit of temperature measure device 66, respectively.

Current delivered through each electrode 16 is measured by currentsensor 62. Voltage between the electrodes 16 is measured by voltagesensor 64. Impedance and power are then calculated at power andimpedance calculation device 60. These values can then be displayed atuser interface 68. Signals representative of power and impedance valuesare received by controller 58.

A control signal is generated by controller 58 that is proportional tothe difference between an actual measured value, and a desired value.The control signal is used by power circuits 56 to adjust the poweroutput in an appropriate amount in order to maintain the desired powerdelivered at the respective electrode 16.

In a similar manner, temperatures detected at thermal sensors 24 and 26provide feedback for maintaining a selected power. The actualtemperatures are measured at temperature measurement device 66, and thetemperatures are displayed at user interface 68. Referring now to FIG.10(h), a control signal is generated by controller 59 that isproportional to the difference between an actual measured temperature,and a desired temperature. The control signal is used by power circuits57 to adjust the power output in an appropriate amount in order tomaintain the desired temperature delivered at the respective sensor 24or 26.

Controller 58 can be a digital or analog controller, or a computer withsoftware. When controller 58 is a computer it can include a CPU coupledthrough a system bus. On this system can be a keyboard, a disk drive, orother non-volatile memory systems, a display, and other peripherals, asare known in the art. Also coupled to the bus are a program memory and adata memory.

User interface 68 includes operator controls and a display. Controller58 can be coupled to imaging systems, including but not limited toultrasound, CT scanners and the like.

Current and voltage are used to calculate impedance. Diagnostics can beperformed optically, with ultrasound, CT scanning, and the like.Diagnostics are performed either before, during and after treatment.

The output of current sensor 62 and voltage sensor 64 is used bycontroller 58 to maintain the selected power level at electrodes 16. Theamount of RF energy delivered controls the amount of power. A profile ofpower delivered can be incorporated in controller 58, and a pre-setamount of energy to be delivered can also be profiled.

Circuitry, software and feedback to controller 58 result in processcontrol, and the maintenance of the selected power that is independentof changes in voltage or current, and are used to change, (i) theselected power, including RF, ultrasound and the like, (ii) the dutycycle (on-off and wattage), (iii) bipolar energy delivery and (iv) fluiddelivery, including chemotherapeutic agents, flow rate and pressure.These process variables are controlled and varied, while maintaining thedesired delivery of power independent of changes in voltage or current,based on temperatures monitored at thermal sensors 24 and 26 at multiplesites.

Controller 58 can be microprocessor controlled. Referring now to FIG.11, current sensor 62 and voltage sensor 64 are connected to the inputof an analog amplifier 70. Analog amplifier 70 can be a conventionaldifferential amplifier circuit for use with thermal sensors 24 and 26.The output of analog amplifier 70 is sequentially connected by an analogmultiplexer 72 to the input of analog-to-digital converter 74. Theoutput of analog amplifier 70 is a voltage which represents therespective sensed temperatures. Digitized amplifier output voltages aresupplied by analog-to-digital converter 74 to a microprocessor 76.Microprocessor 76 may be a type 68HCII available from Motorola. However,it will be appreciated that any suitable microprocessor or generalpurpose digital or analog computer can be used to calculate impedance ortemperature.

Microprocessor 76 sequentially receives and stores digitalrepresentations of impedance and temperature. Each digital valuereceived by microprocessor 76 corresponds to different temperatures andimpedances.

Calculated power and impedance values can be indicated on user interface68. Alternatively, or in addition to the numerical indication of poweror impedance, calculated impedance and power values can be compared bymicroprocessor 76 with power and impedance limits. When the valuesexceed predetermined power or impedance values, a warning can be givenon interface 68, and additionally, the delivery of RF energy can bereduced, modified or interrupted. A control signal from microprocessor76 can modify the power level supplied by power supply 54.

An imaging system can be used to first define the volume of the tumor orselected mass. Suitable imaging systems include but are not limited to,ultrasound, CT scanning, X-ray film, X-ray fluoroscope, magneticresonance imaging, electromagnetic imaging and the like. The use of suchdevices to define a volume of a tissue mass or a tumor is well know tothose skilled in the art.

Specifically with ultrasound, an ultrasound transducer transmitsultrasound energy into a region of interest in a patient's body. Theultrasound energy is reflected by different organs and different tissuetypes. Reflected energy is sensed by the transducer, and the resultingelectrical signal is processed to provide an image of the region ofinterest. In this way, the volume to be ablated is ascertained.

Ultrasound is employed to image the selected mass or tumor. This imageis then imported to user interface 68. The placement of electrodes 16can be marked, and RF energy delivered to the selected with priortreatment planning. Ultrasound can be used for real time imaging. Tissuecharacterization of the imaging can be utilized to determine how much ofthe tissue is heated. This process can be monitored. The amount of RFpower delivered is low, and the ablation or hyperthermia of the tissueis slow. Desiccation of tissue between the tissue and each needle 16 isminimized by operating at low power.

The following examples illustrate the use of the invention with two RFtreatment apparatus with two electrodes shown in FIG. 12, or a pair oftwo electrodes, that are used in a bipolar mode to ablate tissue.

EXAMPLE 1

Exposed electrode length: 1.5 cm

Distance between electrodes: 1.5 cm

Power setting: 5 W

Ablation time: 10 min.

Lesion size:

width: 2 cm

length: 1.7 cm

depth: 1.5 cm

EXAMPLE 2

Exposed electrode length: 1.5

Distance between electrodes: 2.0

Power setting: 7.0

Ablation time: 10 min.

Lesion size:

width: 2.8 cm

length: 2.5 cm

depth: 2.2 cm

EXAMPLE 3

Exposed electrode length: 2.5 cm

Distance between electrodes: 2.0 cm

Power setting: 10 W

Ablation time: 10 min

Lesion size:

width: 3.0 cm

length: 2.7 cm

depth: 1.7 cm

EXAMPLE 4

Exposed electrode length: 2.5 cm

Distance between electrodes: 2.5 cm

Power setting: 8 W

Ablation time: 10 min.

Lesion size:

width: 2.8 cm

length: 2.7 cm

depth: 3.0 cm

EXAMPLE 5

Exposed electrode length: 2.5 cm

Distance between electrodes: 2.5 cm

Power setting: 8 W

Ablation time: 12 min.

Lesion size:

width: 2.8 cm

length: 2.8 cm

depth: 2.5 cm

EXAMPLE 6

Exposed electrode length: 2.5 cm

Distance between electrodes: 1.5 cm

Power setting: 8 W

Ablation time: 14 min.

Lesion size:

width: 3.0 cm

length: 3.0 cm

depth: 2.0 cm

EXAMPLE 7

With return electrode at 1.5 cm

Exposed electrode length: 2.5 cm

Distance between electrodes: 2.5 cm

Power setting: 8 W

Ablation time: 10 min.

Lesion size:

width: 3.0 cm

length: 3.0 cm

depth: 3.0 cm

EXAMPLE 8

Exposed electrode length: 2.5 cm

Distance between electrodes: 2.5 cm

Power setting: low

Ablation time: 12 min.

Lesion size:

width: 3.5 cm

length: 3.0 cm

depth: 2.3 cm

EXAMPLE 9

Exposed electrode length: 2.5 cm

Distance between electrodes: 2.5 cm

Power setting: 11 W

Ablation time: 11 min.

Lesion size:

width: 3.5 cm

length: 3.5 cm

depth: 2.5 cm

EXAMPLE 10

Exposed electrode length: 3.0 cm

Distance between electrodes: 3.0 cm

Power setting: 11 W

Ablation time: 15 min.

Lesion size:

width: 4.3 cm

length: 3.0 cm

depth: 2.2 cm

EXAMPLE 11

Exposed electrode length: 3.0 cm

Distance between electrodes: 2.5 cm

Power setting: 11 W

Ablation time: 11 min.

Lesion size:

width: 4.0 cm

length: 3.0 cm

depth: 2.2 cm

EXAMPLE 12

Exposed electrode length: 4.0 cm

Distance between electrodes: 2.5 cm

Power setting: 11 W

Ablation time: 16 min.

Lesion size:

width: 3.5 cm

length: 4.0 cm

depth: 2.8 cm

EXAMPLE 13

Two pairs of electrodes (Four electrodes)

Exposed electrode length: 2.5 cm

Distance between electrodes: 2.5 cm

Power setting: 12 W

Ablation time: 16 min.

Lesion size:

width: 3.5 cm

length: 3.0 cm

depth: 4.5 cm

EXAMPLE 14

Two pairs of electrodes (Four electrodes)

Exposed electrode length: 2.5 cm

Distance between electrodes: 2.5 cm

Power setting: 15 W

Ablation time: 14 min.

Lesion size:

width: 4.0 cm

length: 3.0 cm

depth: 5.0 cm

Referring to the drawings, FIG. 13 is a planar view of a stylet ablationdevice of this invention. The device comprises a handle portion 112 anda delivery tube portion 114. Stylet sleeve control manual tab 116 andstylet electrode control manual tab 118 are mounted for slidingengagement in slots and in the handle top plate. Index markings 121indicate the relative angle of orientation of the stylet with respect tothe stylet angle indicator 123.

FIG. 14 is a cross-sectional view of the tip of the stylet ablationdevice such as that shown in FIG. 13 with the electrode and sleeveextended. This embodiment shows a flexible stylet 150 having apredetermined curved configuration. The flexible stylet can also bestraight, if the remote position can be reached by a straight path fromthe point of entry without damaging a vital body component. Theelectrode can be made of a shape memory alloy, shaped to the revert to adesired configuration when released from the tubing. The configurationcan be simple curves, a combination of straight portions and curves,curves with differing radii, in two or three dimensions, selected todirect the electrode and its surrounding flexible, highly conformablesleeve in a preselected two or three dimensional path through tissue toa site to be ablated.

A method of this invention for medical ablation of difficult to accesstissues comprising first inserting a hollow needle through a tissuelayer, the needle enclosing a conductive electrode of highly flexiblememory metal having a predetermined curved memory configuration and asharpened distal terminus, the electrode tube being enclosed within aninsulating sleeve axially moveable thereon and bendable therewith. Thenthe electrode and sleeve are advanced from the terminal end of thehollow needle, whereby the portion of the electrode and sleeve advancedbeyond the end of the needle adopt the predetermined curved memoryconfiguration and the electrode and sleeve follow a correspondinglypredetermined curved path through tissue to the site to be ablated. Thena portion of the sleeve is withdrawn from the terminus of the electrodeto expose a predetermined electrode area for ablation. Finally, RFenergy is applied to the tissue surround the exposed electrode area toeffect ablation thereof.

Referring to FIG. 15, use of an embodiment with a shape memory electrodepreformed into a curved shape to ablate a near zero access area behindan obstruction in the body. The objective of the treatment is to reducethe size of the mass 154 behind a rigid obstacle such as bone 156 (orarea to be protected from penetration). The electrical conductor andsleeve is extended from the needle 140 through surrounding tissue aroundthe obstacle to its back surface, and the target tissue to be reduced.The sleeve 136 is then withdrawn to a position exposing the electrodearea required to ablate the tissue mass. Heat is generated in the targettissue from an electric current or electromagnetic field produced by theelectrical conductor. Preferably, the volume of tissue being treated iscontrolled by moving the non-conductive sleeve to expose a selectedlength of electrode in the body tissue to be treated, the remaining areaof the electrode remaining shielded by the sleeve to protect theintervening tissues. The amount and duration of the energy delivery isalso varied to control the volume of tissue being treated. The currentpasses to a large surface area grounding plate contacting the outer skinsurface.

The foregoing description of preferred embodiments of the presentinvention has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise forms disclosed. Obviously, many modificationsand variations will be apparent to practitioners skilled in this art.The embodiments were chosen and described in order to best explain theprinciples of the invention and its practical application, therebyenabling others skilled in the art to understand the invention forvarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the following claims and their equivalents.

What is claimed is:
 1. A tissue ablation apparatus, comprising:anelongated delivery device with a tissue piercing distal end and aproximal end; an RF electrode with a tissue piercing distal tip, the RFelectrode being positionable in the delivery device as the deliverydevice is advanced through tissue, the RF electrode having anon-deployed state when positioned in the delivery device and a deployedstate with curvature as the RF electrode is advanced from the deliverydevice into a selected tissue site; and an electrode advancement membercoupled to the RF electrode for advancing the RF electrode out of theelongated delivery device, wherein the elongated delivery device, the RFelectrode and the electrode advancement member form an integral unit. 2.The apparatus of claim 1, further comprising:an electrode advancementstop that prevents advancement of the RF electrode beyond apredetermined distance.
 3. The apparatus of claim 1, furthercomprising:an electrode stop that prevents removal of the RF electrodefrom the elongated delivery device.
 4. The apparatus of claim 3, whereinthe electrode stop prevents the RF electrode from being removable fromthe elongated delivery device as the elongated delivery device isadvanced through tissue.
 5. The apparatus of claim 1, wherein the RFelectrode includes a fluid delivery lumen.
 6. The apparatus of claim 1,further comprising:an insulator positioned in a surrounding relation toat least a portion of the elongated delivery device.
 7. A tissueablation apparatus, comprising:an elongated delivery device with atissue piercing distal end and a proximal end; an RF electrode with atissue piercing distal tip, the RF electrode being positionable in thedelivery device as the delivery device is advanced through tissue, theRF electrode having a non-deployed state when positioned in the deliverydevice and a deployed state, wherein in the deployed state and RFelectrode distal end exhibits a changing direction of travel as the RFelectrode is advanced from the delivery device into a selected tissuesite; and an electrode advancement member coupled to the RF electrodefor advancing the RF electrode out of the elongated delivery device. 8.The apparatus of claim 7, wherein in the deployed state the RF electrodeincludes curve sections with different radii.
 9. The apparatus of claim7, wherein in the deployed state the RF electrode includes at least onecurved portion and at least one straight portion.
 10. The apparatus ofclaim 7, further comprising:an electrode advancement stop that preventsadvancement of the RF electrode beyond a predetermined distance.
 11. Theapparatus of claim 7, further comprising:an electrode stop that preventsremoval of the RF electrode from the elongated delivery device.
 12. Theapparatus of claim 11, wherein the electrode stop prevents the RFelectrode from being removable from the elongated delivery device as theelongated delivery device is advanced through tissue.
 13. The apparatusof claim 7, wherein the RF electrode includes a fluid delivery lumen.14. The apparatus of claim 7, further comprising:an insulator positionedin a surrounding relation to at least a portion of the elongateddelivery device.
 15. The apparatus of claim 7, wherein the RF electrodeis deployable with curvature from the elongated delivery device.
 16. Theapparatus of claim 7, wherein the RF electrode exhibits a changingdirection of travel as the RF electrode is advanced from the deliverydevice into a selected tissue site with a single radius of curvature.17. A tissue ablation apparatus, comprising:an elongated delivery devicewith a tissue piercing distal end and a proximal end; an RF electrodewith a tissue piercing distal tip, the RF electrode being positionablein the delivery device as the delivery device is advanced throughtissue, the RF electrode having a non-deployed state when positioned inthe delivery device and a deployed state with curvature as the RFelectrode is advanced from the delivery device into a selected tissuesite; an electrode advancement member coupled to the RF electrode andthe handpiece; and a handpiece coupled to the elongated delivery deviceproximal end, the handpiece having a proximal end sufficiently closed toinhibit removal of the RF electrode from the elongated delivery device.18. A tissue ablation apparatus, comprising:an elongated delivery devicewith a tissue piercing distal end and a proximal end; an RF electrodewith a tissue piercing distal tip, the RF electrode being positionablein the delivery device as the delivery device is advanced throughtissue, the RF electrode having a non-deployed state when positioned inthe delivery device and a deployed state with curvature as the RFelectrode is advanced from the delivery device into a selected tissuesite, the RF electrode being non-removable from the elongated deliverydevice as the elongated delivery device is advanced through tissue; andan electrode advancement member coupled to the RF electrode foradvancing the RF electrode out of the elongated delivery device.